Molecular beam focusing devices



April 1960 F.H. REDER 2,933,646

MOLECULAR BEAM FOCUSING DEVICES Filed May 6, 1958 INVENTOR, FRIEDRICH H REDER.

ATTOR/l/EX to the focusing action.

United States Patent;

MOLECULAR BEAM FOCUSING DEVICES Friedrich H. Reder, Lon Branch, N.J., assignor to the United States of America as represented by the Secretary of the Army a 1 Application May 6, 1958, Serial No. 733,456

' '3' Claims. c1. 315-111 (Granted under Title 35, US. Code .1952), sec. 266) state into a beam. This beam is. passed into a cavity,

resonator where, during transitions of the molecules to lower energy states, oscillations of characteristic frequencies, called transition frequencies, are radiated; The resonator is tuned to one of these frequencies, so that the latter is sustained. Amore detailed description of the Maser may be found in Physical Review, vol. 99, Aug. 15, 1955.

One type of focuser, known as the Stark focuser, con- 1 sists'of a plurality of straightmetal rods, evenly spaced along the circumference of a cylinder. Alternate rods are connected to one terminal of a source of high unidijrectional potential, while the intervening rods are connected to the other terminal of said source. A more detailed description of the Stark focuser may be found in Physical Review, vol. 99, Aug. 15, 1955.

A disadvantage of the conventional straight-rod focuser is that molecules etfusing close to the axis of the focuser assembly and parallel to said axis are not acted on by the focuser because in the nozzle a slight flow of the gas is created. This flow causes a substantial number of. molecules to follow a straight path into the focuser and of these molecules'a substantial portion remain in the axial region of the focuser. As a result, these molecules form a useless load since they do not contribute to the power output of the Maser, while they do cause dielectric 'detuning of the cavity.

- In accordance with the present invention, the above Patented Apr. 19, 1950 rods 14, in this case four pairs. Ordinarily these rods are straight and are spaced about a cylinder as indicated by the broken line 16. In the present case, however,

7 these rods are slightly bent so as to form a gradually curved enclosure. As shown in Fig. 2, alternate rods are connected to a lead 18 to which one terminal of a source of unidirectional polarizingpotential is connected.

The intervening rods are connected to the opposite terminal of said source through a lead 20.

. The amount of curvature is such that the projection of the axis of the gun 10, as indicated by thedot-dash line, just misses the output aperture of the focuser. Thus, if the gas is elfused from the gun along a rectilinear path, said path would extend just outside the space bounded by the focuser at the output end thereof. As a result every part of the gas beam is'displaced from the focuser axis at some point and can be more effectively subjected to the action of the focuser.

The molecular beam passes from the focuser into a cavity resonator 22 which functions in the usual manner. While there 'has been described what is at present considered a preferred embodiment of the invention, it

will be obvious to those skilled in the art that various I changes and modifications may be made therein without departing from the invention; and it is aimed in the ap pended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. In a Maser system having a gas eifusing element and a cavity resonator, a Starkfocuser between said gas eifusing element and resonator comprising an even number of like rods evenly spaced about a circle and forming an enclosure into which gas particles are eifused along a rectilinear path, said rods being curved relative to the axis of said path along a radius common to all the rods to form a curved cylindrical enclosure intowhich the molecules pass and a direct current voltage source the terminals of which are connected to said rods to impart opposite polarity to adjacent rods.

2 In a Maser, a Stark type focuser structure, means ,path extending into said focuser, at least a portion of the ,eifects are reduced by slightly curving the focuser'assembly so that the straight projection of axis of the gun through which the molecular stream is ejected just misses the output aperture of the focuser. In this way almost all the molecules are at some point substantially displaced -from the axis of the focuser and 'are subjected For a'better understanding ofgthe invention, together with other and further objects thereof, reference is bad to the following description taken in connection with the accompanying drawing, in which:

Fig. l is a perspective view of a focuser and cavity of a Maser built in accordance with the invention; and

Fig. 2 is a section taken along line 2'--2 of Fig. 1. In'Fig. 1, the mouth of the usual gun or eifuser 10 efiuses a stream of ammoniagas molecules into the focuser 12. The focuser comprises a plurality of pairs of axis of said focuser being inclined along a plane parallel to said axis relative to said path forming a curved inclosure into which the molecules pass and a cavity resonator at the output of said focuser to receive molecules passing out of said focuser.

3. In a Maser as set forth in claim 2, wherein said focuser structure comprises, an even number of evenlyspaced curved rods defining the space through which said molecules are directed, the length and degree of curvature of said rods being such thatsaid rectilinear path just falls outside of said space near the output end of said focuser.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Molecules and Microwaves" in Electronic and Radio Engineer, July 1957, pages 254 to 257. 

